Biosynthesis of thalicarpine

Abstract

The incorporation of (±)-, norlaudanosoline, −nor-reticuline, −N-methylcoclaurine and −norlaudanidine into thalicarpine in Cocculus laurifolius DC has been studied and specific utilization of (±)- reticuline is demonstrated. The evidence supports that both the “halves” of thalicapine are derived from reticuline. Parallel feedings of ( S)-, and ( R)-, reticulines showed that the stereospecifity is maintained in the biosynthesis of thalicarpine from the 1-benzyl-tetrahydroisoquinoline precursor. A double-labelling experiment with (±)-[1- 3H, 4′-O 14CH 3] nor-reticuline has shown that the 4′OMe group of a nor-reticuline unit is lost in the biotransformation into thalicarpine. Feeding experiments also revealed that the plants can convert ( S)-bolding and ( S)-isoboldine into thalicarpine.